Chillers, which are used to cool vast interior spaces such as airport terminals, shopping malls and officer towers, include vapor compression systems that generally comprise a refrigeration loop and a lubrication loop. The refrigeration loop includes a condenser, an expansion device, an evaporator or cooler, and a compressor. The lubrication loop also includes the compressor and is designed to provide lubrication to the compressor. Because the refrigeration loop and the lubrication loop intersect in the compressor, liquid refrigerant from the refrigeration loop and lubricant from the lubrication loop are allowed to intermingle resulting in a mixture of liquid refrigerant and lubricant. The lubricant-refrigerant mixture collects in the evaporator, where it may degrade the heat transfer capability of the system if not reclaimed. Because the viscosity of the refrigerant is much lower than the viscosity of the lubricant, the lubricant-refrigerant mixture formed has a viscosity that is much lower than necessary for adequate lubrication of the compressor. Therefore, upon reclamation, the lubricant-refrigerant mixture may not be suitable for use as a lubricant.
Accordingly, known chillers incorporate a generator vessel or a still to address this concern. The still, which is actually a concentrator, functions to remove the oily refrigerant from the evaporator and to separate the lubricant from the liquid refrigerant. Conventional stills accomplish this by boiling off the refrigerant through the addition of heat, leaving an oil-rich mixture with a high enough viscosity as to be suitable for use as a lubricant. However, at some pressure-temperature conditions encountered by chillers, it can be difficult to develop adequate lubricant viscosity by the conventional method of adding heat. Furthermore, even if adequate lubricant viscosity can be achieved by heat addition alone, to achieve this viscosity would require the addition of a substantial amount of heat resulting in an undesirable reduction of chiller energy efficiency.
As such, there is a desire for a lubrication reclamation system that is operable to remove refrigerant from a lubricant-refrigerant mixture without the substantial heat input required by traditional systems.